The purpose of this document is to provide guidelines to assure that boiler tubes for new construction and replacement, both in recovery and other boilers, are metallurgically sound and free from potentially harmful defects. Special emphasis is placed on obtaining tubing of appropriate quality for critical recovery boiler service. This service is defined as that in which tube leaks or failures can directly or indirectly lead to water reaching the smelt bed in the furnace, thereby creating the risk of explosion. Noncritical service encompasses all other recovery boiler tubing and power boiler tubing where leakage can result in increased safety risk or significant service interruption. This document covers boiler tube materials specified in the American Society for Mechanical Engineers (ASME) Boiler and Pressure Vessel Code Section II, Part A. Similar specifications are issued by the American Society for Testing and Materials (ASTM).